somebody asked:
Hello everybody. I´m learning about pest control by the hard way...I
recently lost some junipers from phomopsis. It´s a bitter path for
learning about integrated pest control. So I´m still learning and
need some advice in planing a schedule/calendar for use of pesticides
around the year. Is there a correct/optimal way for use them
preeemptive. You have to consider, for instance the phomopsis
infection: for sure are all trees now infected, but I will see it
next spring, so I´ll have to make some treatment from end autumn or
begining spring.

The first step in preemption is to learn what you need to worry about.
If you don't have insect problems, you don't need to worry until a
specific insect is likely to be a problem. For me on Long Island, the
problem was pine tip borers: I lived in the middle of a pine barren, so
I could be sure I'd always have to worry about them. So I read up on
them, learned their life cycle and when they'd be laying their eggs in
my region, then I took action to prevent it. I could have sprayed the
trees with a protectant, but insects laying eggs aren't as deterred by
insecticides because they aren't eating, they're using the other end.
So I covered my plants with mesh during the egg-laying season.
Effective for me. (However, someone who heard me describe this used it
herself and it didn't work; when I talked to her later, it was clear
her problem wasn't pine borers, but some other insect).

Fungi should be treated the same way: only worry about what you've
identified as a problem. Some have an infective season, so you can
protect your trees by spraying them in that season, or else protect
them by moving them to a safe place (in the case of pathogens that
infect during the wet springtime, you can simply keep the plants dry).
Something like Phomopsis doesn't have a specific season (on the east
coast of the US, that is. I can't speak for Chile), so you have to
take other measures, unless you want to be spraying every week for the
rest of your tree's life. Phomopsis is not a deadly disease: if you
have dieback from it, just prune off the diseased branches and keep the
foliage dry until you're sure you've removed it all. Sterilize pruning
wounds, and from now on, make sure you don't prune in wet weather or on
wet foliage. Phomopsis is most likely to occur if you have stressed
trees, so keep yours well-watered and fertilized, and the trees should
be able to fight it off themselves.

Finally, if some pest problem is very severe, I'd give up on that
species of plant and grow something else. Bonsai shouldn't be that
hard; grow plants that grow well in your environment.

Nina